Global disabling of shadows in Cycles
That Cycles checkbox only disables transparent shadows, hence it's location next to the transparent depth controls. It has no affect on regular shadows from material without the transparent BSDF, and even materials with the Transparent BSDF will still cast shadows with it disabled. Just without taking transparency into account.

There is no global control to disable shadows, you need to disable shadow-ray visibility on all objects. If you need to do it for a lot of objects, the following bit of Python will switch off the checkbox for all selected objects:

import bpy

for obj in bpy.context.selected_objects:
    bpy.context.scene.objects.active = obj
    bpy.context.object.cycles_visibility.shadow = False